You have a down day and it's followed by an up day, that's how negotiations go…. Thus the chairman of Barcelona's closing plenary session summarized a roller coaster week.

Strong words were uttered in Barcelona as tensions built over who should do what between developing and industrial nations. The source of most friction is the fate of the Kyoto Protocol — developing nations don't want to give up Kyoto without a strong commitment to a new and stronger agreement.

African nations actually walked out of a session Monday, stalling one track of talks for 24 hours. By Thursday some participants were lowering expectations for a climate treaty in December altogether.

But if Thursday was a down day, we bounced back Friday. In the closing plenary, instead of fireworks, nations took the microphone, one after the other, reiterated their positions and then stated their deep commitment to reaching a strong outcome in Copenhagen, establishing or leading to a firm and binding global climate treaty.

Not that all tensions were resolved. Far from it. Some nations are calling for a single agreement, others for a two track outcome — where Kyoto would continue until a stronger global treaty can be reached.

But if Friday was an up day, there is certainly more excitement to come.